counting and loops

hello

i need help with programming a module that will count a column by comparing the value after it and saving the number of rows it counted before a different value occured in addition with saving the row number to a variable at the row right before the different value occured.
this will occur throughout the whole column

example

245
245
245
245
245
250
250
250
260
260
so the loop (as i would imagine) would count the number of rows for 245 which is 5 and say it occured on row 26 which will save row 26 to some variable then it will count 250 which is 3 and so forth

any help would be greatly appreciated